Lubricating oil compositions

ABSTRACT

ANTIOXIDANT ADDITIVES FOR LUBRICATING OILS AND LUBRICATING OIL COMPOSITIONS CONTAINING SAID ANTIOXIDANT ADDITIVES. THE STABILITY OF LUBRICATING OIL COMPOSITION TOWARD OXIDIZING CONDITION IS MARKEDLY IMPROVED WHEN AN ANTIOXIDANT ADDITIVE COMPRISING A MIXTURE OF A METAL DIALKYLDITHIOCARBAMATE AND A TERTIARYALKYL PRIMARU A,OME IS INCORPORATED THEREIN. THE PREFERRED ADDITIVES COMPRISE CADMIUM DIAMYLDITHICARBAMATE OR ANTIMONY DIALKYLDITHIOCARBAMATE PLUS A MIXTURE OF C18 TO C22 TERTIARY-ALKYL PRIMARY AMINES.

3,70 7,48 Patented Dec. 26, 1972 3,707,498 LUBRICATENG OIL COMPOSITIONS Daniel Milsom. Hightstowu, N.J., assignor to Cities Service Oil Company No Drawing. Filed Oct. 30, 1970, Ser. No. 85,745 Int. Cl. (110m 1/32, 1/38 US. Cl. 252-33.6 13 Claims ABSTRACT OF THE DISCLOSURE Antioxidant additives for lubricating oils and lubricating oil compositions containing said antioxidant additives. The

stability of lubricating oil compositions toward oxidizing conditions is markedly improved when an antioxidant additive comprising a mixture of a metal dialkyldithiocarbamate and a tertiaryalkyl primary amine is incorporated therein. The preferred additives comprise cadmium diamyldithiocarbamate or antimony dialkyldithiocarbamate plus a mixture of C to C tertiary-alkyl primary amines.

BACKGROUND OF THE INVENTION Engine lubricating oils are used under conditions whereby they are subjected to oxidative degradation. Under oxidizing conditions, the hydrocarbon molecules of a lubricating oil may undergo a number of undesirable reactions. For example, the hydrocarbon molecules may under go polymerization to thereby cause an increase in the viscosity of the oil. In addition, polymerization may proceed to the point where insoluble polymerizates are formed, thus resulting in sludge formation. Also, acidic oxygen-containing products may be formed. Such acidic materials tend to cause corrosion and wear.

It is taught in the prior art that oxidative degradation of hydrocarbon lubricating oils may be prevented by the addition thereto of various antioxidant additives. Examples of antioxidants used in the prior art are hindered amines, hindered phenols, and metal dialkyldithiocarbamates. However, the antioxidant additives become exhausted after a time and oxidative degradation of the hydrocarbon lubricating oil may commence. The time until an antioxidant becomes exhausted may, of course, be extended by the use of larger quantities of the additive. However, the amount of additive used is limited by economic considerations and by its solubility in the hydrocarbon lubricating oil.

SUMMARY OF THE INVENTION It is an object of this invention to provide antioxidant additives for hyrocarbon lubricating oils that are effective at low concentrations.

It is another object of this invention to provide antioxidant additives for hydrocarbon lubricating oils that are ehective for extended periods of time.

It is yet another object of this invention to provide bydrocarbon lubricating oil compositions that are resistant to oxidative degradation for long periods of time.

Other objects will be apparent to those skilled in the art in view of this disclosure.

These and other objects are obtained by the practice of my invention. In general, my invention comprises an antioxidant additive for hydrocarbon lubricating oils comprising a metal dialkyldithiocarbamate and a tertiaryalkyl primary amine; and hydrocarbon lubricating oil compositions comprising a major proportion of a hydrocarbon lubricating oil and a minor proportion of a mixture of a metal dialkyldithiocarbamate and a tertiary-alkyl primary amine.

Therefore, according to the practice of my invention, economical antioxidant additives for hydrocarbon lubricating oils are obtained that are effective at low concentrations and for extended periods of time. Lubricating oil compositions containing the antioxidant additives of this invention are resistant to oxidative degradation for extend ed periods of time as evidenced by resistance to viscosity increase, sludge formation, and increase in acid number.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The antioxidant additives of my invention comprise mixtures of metal dialkyldithiocarbamates and tertiaryalkyl primary amines. Metal dialkyldithiocarbamates and tertiary-alkyl primary amines are known and used individually as antioxidants in lubricating oils. However, I have discovered that when a mixture of a metal dialkyldithiocarbamate and a tertiary-alkyl primary amine is incorporated in a hydrocarbon lubricating oil there is an unexpectedly enhanced resistance of the lubricating oil to oxidative degradation.

The metals usually associated with the dialkyldithiocarbamates are from Groups IIb, IVa, and Va of the Periodic Table. The preferred metals are zinc, cadmium, lead, and antimony. Each of the alkyl groups of the metal dialkyldithiocarbamate will contain from about 3 to about 10 carbons and may be straight chain or branched. The two alkyl groups in any one metal dialkyldithiocarbamate molecule may be either the same or different. Examples of suitable metal dialkyldithiocarbamates are zinc di-n-butyldithiocarbamate, zinc diamyldithiocarbamate, lead diamyldithiocarbamate, cadmium dipropyldithiocarbamate, antimony propyloctyldithiocarbamate, cadmium hexyldecyldithiocarbamate zinc heptylnonyldithiocarbamate, lead diheptyldithiocarbamate, zinc isopropyloctyldithiocarbamate, lead isobutylnonyldithiocarbamate, tin diisobutyldithiocarbamate, tin hexylnonyldithiocarbamate, bismuth dioctyldithiocarbamate, bismuth isoamylheptyldithiocarbamate, bismuth didecyldithiocarbamate, antimony isoamyldecyldithiocarbamate, and antimony dioctyldithiocarbamate. The preferred dialkyldithiocarbamates are cadmium diamyldithiocarbamate and a 50 weight percent solution in oil of an antimony dialkyldithiocarbamate manufactured by R. T. Vanderbilt Company, Inc. under the tradename of Vanlube 73.

The tertiary-alkyl primary amine component of my antioxidant additive has about 8 to about 30 carbons and preferably about 12 at about 22 carbons. The amines are saturated and are, of course, characterized in that they are primary-amines in which the amino nitrogen is attached to a tertiary-carbon of an alkyl group. It is contemplated that the tertiary-alkyl primary amine component of my additive may be either a single tertiary-alkyl primary amines. Examples of suitable amines are tertiaryoctylamine; l-methyl-l-ethyl-n-dodecylamine; 1,l,3,3,5,5- hexaethyl-n-hexylamine; 1,l-dimethyl-n-decylamine; 1,1, 3,3,5,S-hexapropyl-n-hexylamine; and 1,1-dinonyl-n-dodecylamine. The preferred amines are a mixture of C to C tertiary-alkyl primary amines manufactured by Rohm & Haas under the tradename Primene 814R and a mixture of C to C tertiary-alkyl primary amines manufactured by Rohm & Haas under the tradename Primene JM-T.

The antioxidant additive of my invention contains tertiary-alkyl primary amine and metal dialkyldithiocarbamate at a weight ratio of about 0.5 :1 to 10:1, and preferably about 1:1 to 9:1, amine to carbamate. In the case where the additive is a mixture of Primene JM-T and cadmium diamyldithiocarbamate, an especially preferred weight ratio is within the range 2:1 to 5:1. In the case where the additive is a mixture of Primene JM-T and the antimony dialkyldithiocarbamate manufactured by R. T. Vanderbilt Company under the trade name Vanlube 73, an especially preferred weight ratio is within the range 2:1 to 7: 1.

The hydrocarbon lubricating oil compositions of my invention comprise a major proportion of hydrocarbon lubricating i1 and a minor proportion, usually about 0.5 to 4.5 weight percent, and preferably about 1.0 to 3.5 weight percent, of the inventive antioxidant additive. In the case where the additive is a mixture of Primene JM-T and cadmium diamyldithiocarbamate, the lubricating oil composition comprises a major portion of hydrocarbon oil and about 1.0 to 2.5 weight percent of additive. In the case where the additive is a mixture of Primene IM-T and Vanlube 73 which is 50 weight percent of an antimony dialkyldithiocarbamate in oil, the lubricating oil composition comprises a major portion of hydrocarbon oil and about 1.0 to 3.5 weight percent of the active ingredients of the additive.

The efficacy of the antioxidant additives of my invention is' determined by subjecting hydrocarbon lubricating oil compositions containing the additives to a catalyzed oxidation test. In the test, a sample of the hydrocarbon lubricating oil composition to be tested has added thereto 1000 ppm. of a particulate catalyst having a particle size of about microns and consisting of 1 part of copper, 1 part of bronze, 1 part of babbit, and 2 parts of iron. The mixture is stirred at 300 F., and the viscosity of the lubricating oil composition at 210 F. is determined at intervals. The test is stopped and the time recorded when the viscosity 0 fthe lubricating oil composition at 210 F. has increased by 2.5 SUS.

The following examples are presented to further illustrate my invention.

EXAMPLE I Several oil compositions are prepared by dissolving antioxidant additives of my invention in a major proportion of a hydrocarbon gas engine oil and the oil compositions are subjected to the catalyzed oxidation test. The additives are comprised of cadmium diarnyldithiocarbamate and the tertiary-alkyl primary amine component is Primene JM-T. For comparison, a base gas engine oil containing no antioxidant and gas engine oil compositions containing cadmium diamyl-dithiocarbamate alone and Primene JMT alone are also subjected to the catalyzed oxidation test. For each oil composition, the end point of the test is the time in hours for the viscosity at 210 F. to increase by 2.5 SUS. The difference in time for each composition relative to the time for the base oil is recorded as A hours. Table I contains the results of the catalyzed oxidation tests and the amount of each compononent of the additive. All percents are weight percents of the total oil compositions.

TABLE I Cadmium diamyl- Primene dithiocarbamate, wt. JM-T, wt. End point, percent percent hrs. A hours The data in Table I illustrate the synergistic antioxidant properties obtained when the antioxidant additive is a tertiary-alkyl primary amine used in conjunction with a metal dialkyldithiocarbamate.

EXAMPLE II 4 II contains the results of the catalyzed oxidation tests and the amount of each component of the additive. All percents are weight percents of the total oil compositions.

TABLE II Antimony dialkyldithioear- Primcne Vanlube 73, wt. bamate,wt. .TMT, wt. End point, percent percent percent hrs. A hours Similar results may be obtained when other metal dialkyldithiocarbamates and tertiary-alkyl primary amines comprise the antioxidant additive. Suitable antioxidant additives may, for example, be obtained by mixing any of zinc di-n-butyldithiocarbamate, zinc diamyldithiocarbamate, or lead diamyldithiocarbamate with any of tertiaryoctylamine, 1-methyl-l-ethyl-n-dodecylamine, or the mixture of C C tertiary-alkyl primary amines marketed by Rohm & Haas under the tradename Primene 81-R.

While the present invention has been described herein with reference to particular embodiments thereof, it will be recognized by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as set forth in the appended claims.

I claim:

1. An antioxidant for hydrocarbon lubricating oils comprising a metal dialkyldithiocarbamate and a tertiary-alkyl primary amine wherein the metal associated with the dialkyldithiocarbamate is selected from the group consisting of metal from Groups IIb, Na, and Va of the Per-iod ic Table and wherein the weight ratio of said tertiaryalkyl primary amine to said metal dialkyldithiocarbamate is from about 0.5:1 to about 10:1.

2. The antioxidant of claim 1 wherein the metal is Selected from the group consisting of zinc, cadmium, lead, and antimony.

3. The antioxidant of claim 2 wherein each alkyl group of the metal dialkyldithiocarbamate contains about 3 to about 10 carbons.

4. The antioxidant of claim 2 wherein the tertiaryalkyl primary amine contains about 8 to about 30 car bons.

5. The antioxidant of claim 4 wherein the tertiaryalkyl primary amine contains about 12 to about 22 carbons.

6. The antioxidant of claim 5 wherein said metal dialkyldithiocarbamate comprises cadmium diamyldithiocarbamate and said tertiary-alkyl primary amine comprises a mixture of C to C tertiary-alkyl primary amines, the weight ratio of said mixture of said amines to cadmium diamyldithiocarbamate being from about 2:1 to about 5:1.

7. The antioxidant of claim 5 wherein said metal dialkyldithiocarbamate comprises an antimony dialkyldithiocarbamate and said tertiary-alkyl primary amine comprises a mixture of C to C tertiary-alkyl primarv amines, the weight ratio of said mixture of amines to antimony dialkyldithiocarbamate being from about 2:1 to about 7:1.

8. A hydrocarbon lubricating oil composition comprising a major proportion of a hydrocarbon lubricating oil and about 0.5% to about 4.5% by weight, based on said hydrocarbon lubricating oil composition, of the additive of claim 1.

9. A hydrocarbon lubricating oil composition comprising a major proportion of a hydrocarbon lubricating oil and about 1.0% to about 3.5% by weight, based on said hydrocarbon lubricating oil composition, of the additive of claim 5.

10. A hydrocarbon lubricating oil composition comprising a major proportion of a hydrocarbon lubricating oil and about 1.0% to about 2.5% by weight, based on said hydrocarbon lubricating oil composition, of the additive of claim 6.

11. A hydrocarbon lubricating oil composition comprising a major proportion of a hydrocarbon lubricating oil and about 1.0% to about 3.5% by weight, based on said hydrocarbon lubricating oil composition, of the additive of claim 7.

12. A hydrocarbon lubricating oil composition comprising a major proportion of a hydrocarbon lubricating oil, about 0.4% by weight of said hydrocarbon lubricating oil composition of cadmium diamyldithiocarbamate, and about 1.0% by wegiht of said hydrocarbon lubricating oil composition of a mixture of C to C tertiary-alkyl primary amines.

13. A hydrocarbon lubricating oil composition compris- References Cited UNITED STATES PATENTS 2,629,694 2/1953 Woods et al 252-335 2,794,781 6/ 1957 Diamond et a1 25233.6 3,462,367 8/1969 Bocher 25233.6 X

DANIEL E. WYMAN, Primary Examiner W. H. CANNON, Assistant Examiner US. Cl. X.R. 252-400 

